Recently, demand for miniaturization or dimensional reduction of electronic apparatuses has increased. As a result, very small-sized chip electronic components are increasingly employed as electronic components. Particularly, very small-sized chip electronic components which are as small as 0.6 mm in length×0.3 mm in width×0.25 mm in thickness are manufactured in recent years.
A conventional chip electronic component is described below using a chip resistor as an example.
FIG. 3 is a perspective view showing the structure of a conventional chip resistor. FIG. 4 is a sectional view of the chip resistor.
In FIG. 3 and FIG. 4, a pair of surface electrode layers 2 are formed at both ends of the surface of a substrate 1 made of 96 alumina substrate. The surface electrode layers 2 are made of a silver cermet thick film electrode. Resistor layer 3 is formed so as to be electrically connected to a pair of surface electrode layers 2, and the resistor layer 3 is made up of ruthenium thick film resistor. Protective layer 4 is formed so as to completely cover the resistor layer 3, and the protective layer 4 is made of an epoxy resin. A pair of side electrodes 5 disposed so as to be electrically connected to the pair of surface electrode layers 2 at both ends of the substrate 1 are made of silver cermet thick film. Nickel plated layers 6 and solder plated layers 7 are formed so as to cover exposed portions of the side electrodes 5 and the surface electrode layers 2. The nickel plated layer 6 and solder plated layer 7 are formed in order to maintain the soldering property of side electrodes of the electronic component. Thus, a chip electronic component comprises external electrodes formed by side electrodes 5, nickel plated layers 6 and solder plated layers 7.
To avoid a change of the resistance during a high temperature firing of silver cermet thick film electrode comprising the above side electrodes 5, there is a proposal of using a conductive paste containing thermosetting resin to form the side electrodes 5 (Japanese Patent Laid-open Publication No. 61-26801).
However, as conductive powder in the above conductive paste, generally used is flake silver powder that may realize a low resistance at a low content. Accordingly, the color of the side electrode becomes white after curing. Since the white color is very similar to the color of 96 alumina substrate which makes the substrate, it is not easy to check the application state of conductive paste. That is, even if the application state of conductive paste is defective, it is difficult to recognize by checking the appearance.
As a means for checking the application state of the conductive paste, a method of checking the application state of conductive paste by using a conductive paste blended with flake silver powder and spherical silver powder is proposed as is disclosed in Japanese Patent Laid-open Publication 8-213203.
However, due to the recent miniaturization of chip electronic components, it is now difficult to recognize the application state of conductive paste by using the above checking method. That is, if the recognition sensitivity is improved in order to prevent the generation of slightly defective application, it becomes difficult to check the application state of conductive paste since the metallic luster of flake silver powder contained in the paste is very similar to the color of 96 alumina substrate which makes the substrate.